ec 2 00 7 A PT - symmetric periodic problem with boundary and interior singularities ∗
نویسندگان
چکیده
1 The general problem class We consider on the interval (−π, π) the singular non-symmetric differential equation Lu := iε d dx f (x) du dx + i du dx = λu, (1.1) in which f is a 2π-periodic function having the following properties: f (x + π) = −f (x) , f (−x) = −f (x) ; (1.2) * We are grateful to Brian Davies for attracting our interest to the problem, and for numerous useful discussions. We also thank John Weir for his comments on an earlier version of this manuscript.
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